Core C Microbiology and Virology. For the past 31 years, the Microbiology and Virology Core has supported the projects of this Program by creating and maintaining an extensive Infectious Diseases (ID) database. This database has been critical for projects that have Infectious Disease endpoints. Over the years the function and services provided by the Core have expanded, mainly driven by the availability of highly sensitive and quantitative diagnostic capabilities, which made it imperative to have standardized definitions and interpretations of diagnostic test results for the Programs. Therefore, all infection endpoints for clinical trials or studies related to the aims of the projects are discussed with the Core director, the Core provides statistical support and data management for specific ID analyses related to the projects. State-of - the-art diagnostic capabilities are provided and continuous efforts are made to improve diagnostic capabilities for pathogens relevant to hematopoietic cell transplant recipients. The Core also maintains a prospective sample collection to facilitate infection diagnosis using research diagnostic assays. In addition, the Core provides monitoring capabilities for immune reconstitution studies. Specifically, the Core provides the following services: 1. State-of-the-art diagnostic molecular capabilities for the detection of occult infections and pathogen quantitation. These assays will be applied in patients with idiopathic pneumonia syndrome and for optimizing BAL and tissue-based quantitative molecular diagnosis. 2. Provision of data management and statistical services to Project and Core leaders. 3. Data entry and quality control of the IDdatabases. 4. Assistance to Project and Core leaders in defining ID endpoints, including assurance of appropriate use of ID database, and assistance in analysis of ID data. 5. Maintaining a tissue sample repository (BAL and blood). 6. Antigen preparation for T cell assays. Relevance to Public Health: This Core will assist Projects by applying new diagnostic tests for infectious agents to samples from patients undergoing allogeneic hematopoietic cell transplantation and by making accurate and consistent diagnoses of infectious complications. The Core will store clinical samples, apply a battery of research diagnostic tests, establish infectious disease diagnoses, and correlate infections with transplant outcomes. These efforts will not only aid this Program Project in achieving its goals, but will likely lead to a better understanding of infectious complications in other immunosuppressed patient populations.